There's a logic to these things. Muammar Gadafy, growing older, and his isolated Libya, growing poorer, were getting nothing worthwhile from the atomic bomb they hadn't built yet or chemicals they had scant residual use for. Logic - and common sense - meant changing tack. Good for logic. But logic doesn't stop there.
What next? If weapons of mass destruction are a menace in unstable regions such as the Middle East, if their availability must be reduced, then logic begins to move us closer to the confrontation we never seek with the nuclear power we - let alone Messrs Bush and Blair - seldom mention: Israel.
Nobody, including the Knesset, quite knows what happens inside the Dimona complex, but if you put together a compote of usually reliable sources (the Federation of American Scientists, Jane's Intelligence Review, the Stockholm Institute), a tolerably clear picture emerges. Ariel Sharon probably has more than 200 nuclear warheads this morning - more if the 17 years since Mordechai Vanunu's kidnapping have been devoted to building stockpiles.
That makes Israel the world's fifth largest nuclear power, boasting more bangs from Washington's bucks than Blair's Britain. And over in the other WMD basket, nobody much dissents when a report by the office of technology assessment for the US Congress concludes that Israel has "undeclared offensive chemical warfare capabilities" and is "generally reported as having an undeclared offensive biological warfare program". Bombs, missiles, delivery systems, gases, germs? Tel Aviv has the lot. We only forget to remember because it's not a suitable subject for polite diplomatic conversation.
Logic, in the old days, didn't trouble too much about that. It saw a state of Israel surrounded by many potential foes who denied its right to exist. It saw such enemies initiate research of their own. It saw too many wars, bitterly fought. It watched the Soviet Union, with warheads to spare, cruising continually in these troubled waters. It was prepared to turn a blind eye and to button its lip.
Come back today for a reality check, though. Saddam's Iraq is a wrecked rat trap. The weapons of mass destruction Gadafy sought are no more, no threat. Yemen, Jordan, Saudi Arabia, Egypt? Nothing to say, nothing to show. You can, if you wish, be concerned about Syria's chemical weapons facilities - and you can reasonably worry about a nuclear Iran, even though Tehran took a decisive step back towards international acceptability last week. But Moscow is out of the action, and the whole dynamic of Middle East danger has changed. Logic comes knocking at Sharon's door.
He faces problems, of course: problems of intractable politics and Palestinian suicide bombers. But he can't nuke Gaza or gas Bethlehem. His WMD are useless in any battle for hearts and minds - as practically useless as Gadafy has just deemed them to be. So why keep Dimona and the biological research center at Nes Ziona out of any equation? Why pretend that they don't exist?
The formal logic of defense is threat, counter-threat. Sit in Tehran and look east - at China, India and Pakistan, with their bombs; look west, and there sits Israel. It is natural, in logic, that Iran consider its own deterrent. It will require a deal of understanding engagement - and guarantees - to close off that path. But such guarantees are possible in the age of the world's only superpower. There is every reason to talk frankly about Israel's bomb, just as the Syrians could be closely involved in dismantling chemical stockpiles if only we could find the right language to start.
What, after all, is the current western fear? Of terrorism, rogue states, of more 9/11s. That's why Geoff Hoon's latest defense review moves out of heavy tanks and battleships. It adjusts to what it calls the new realities of flexibility and intelligence. Even Gadafy seems to have noticed. Why not mention them to Sharon?
An Israel bristling with nuclear hardware it cannot talk about and chemical horrors it could negotiate away does not make itself, or the world, any safer. On the contrary, it makes a hypocritical farce of too much Washington bargaining, buries too many initiatives deep down Hypocrisy Gulch and gives rogue groupings in ex-rogue states every reason to carry on developing, stealing or buying the devices that keep Mr Blair awake at night.
Does Tel Aviv see that connection? Does it want to bring a whole region in from the cold? Such things are becoming possible. But first we need the honesty to follow where logic leads; and begin to talk about them.
© Guardian Newspapers Limited 2003